It's not so much that you want to feed a "light" version of food, but you want to feed a lower carb version of food. Most wet foods will be lower in carbs than any dry food and lower in calories.
I feed the Friskies classic pate style foods except for the Mixed Grill flavor. The Friskies Special Diet pate foods are nice and low in carbs also. Fancy Feast classic pate styles are also good low carb, inexpensive choices, readily available most places in the USA. People also recommend the Wellness grain free canned foods, but I've never tried them as they are too costly for me to feed 3 kitties.
See vet Dr. Lisa Pierson's food chart at catinfo.org and look for choices that are <10% carbs. You don't say where you are from, but if not in the USA or Canada, we have food lists for international members too.
If you mix some additional water into the food, it can help your cat to feel fuller. Think applesauce consistency to even a bit more soupy.
Usually with a diabetic cat, they are losing weight already, since they can't properly process the food without enough insulin.
We strongly recommend that you be home testing before you switch to a lower carb food, as the diet change can dramatically drop the BG (blood glucose) levels and a reduction in the insulin dose is usually required.